Ink applicator



May 31, 1966 w MCDQNOUGH 3,253,542

INK APPLICATOR Filed Aug. 17, 1964 W RESIN I PLASTICIZYER ADDED PLASTISOL SALT ADDED PLASTISOL SALT I MOLD UNDER HEAT SALT FILLED ROLLER FORMED I SALT LEACHED Y POROUS ROLLER 1 INK UNDER VACUUM INKED ROLLER INVENTOR WL [ham ZTJIFDonou ATTORNEYS United States Patent 3,253,542 INK AllPLlCATGR William F. McDonough, Trumbull, Conn., assignor to Pitney-Bowes, Inc, Stamford, Conn., a corporation of Delaware Filed Aug. 17, 1964, Ser. No. 389,876 8 Claims. (Cl. 101-367) This invention relates to a porous ink-impregnated applicator for applying ink to a printing plate or die, and more particularly to such an ink applicator that will maintain its physical characteristics and dimensions over a period of extended usage.

There are a great number of machines in use today which require a printing operation wherein an inked plate or die performs the printing function. Business machines of many types employ such printing functions. Adding machines, 'addresser-printer machines and postage metering machines are typical examples. Generally, in such machines one or more flat or curved printing plates or dies are used to apply thousands of printed impressions over a period of time.

The printing operation of many business machines is intermittent and therefore ink is preferably applied to the printing plate just prior to the making of an impression. Accordingly, the ink applicator must apply the ink uniformly over the printing plate surface whenever the plate is actuated to perform its printing function. If the ink applicator, usually in the form of a roller, does not properly contact the printing plate, there may be too much or too little ink applied to the printing plate or a portion of the plate may remain uninked. Further, if the ink in the ink applicator does not flow properly to the ink transfer surface, the printing plate will be poorly inked when it is actuated. The resiliency and surface texture of the ink applicator should be maintained for the printing of good, uniform impressions. Such problems may occur if the ink tends to dry out on the applicator surface, or to set or harden thereon. In such cases ink will be unevenly transferred to the printing plate, if at all.

Prior art business machines of this type have employed a roller having part of its outer surface immersed in an ink reservoir with an upper part of the roller surface positioned for contact with an intermediate transfer roller which, in turn, is in contact with the printing plate. Thus, rotation of the inking roller carries ink from the reservoir to the intermediate roller which, in turn, transfers it to the printing plate surface. Such prior art approaches, however, have a number of drawbacks including the required periodic filling of the ink reservoir by the user of the machine. A further disadvantage was that atmospheric conditions, cleanliness of the ink transfer roller and like factors determined the amount and the uniformity of the ink which would be transferred from the reservoir to the printing plate.

Another prior art approach has been in the use of fiber rollers for such business machines. These fiber rollers are capable of holding a substantial amount of ink, but tend to lose their physical dimensions and surface characteristics over an extended period of time. Such prior art fiber rollers generally mat down, resulting in a change of physical characteristics of the ink transfer roller. The matting of the fiber reduces the effective diameter of the roller and also changes the surface texture of the roller. Porous ink rollers have also been used, as well as rollers having internal ink reservoirs.

I have found that ink-impregnated rollers made in accordance with my invention eliminate the need for ink reservoirs in such business machines. Since the rollers are relatively inexpensive, they are disposable when their ink supply is depleted or, alternatively, such rollers can 3,253,542 Patented May 31, 1966 be impregnated with ink. I have further found that inkimpregnated porous rollers made in accordance with my invention 'will maintain their physical dimensions and characteristics over an extended period of time in use. My roller will not mat down at the surface, but will remain resilient with good ink transferring characteristics for thousands of ink transfer operations over an extended period of time.

Accordingly, it .is an object of the present invention to provide a porous ink-impregnated applicator for repeatedly applying ink to a printing plate over an extended period of time.

Another object of the invention is to provide an applicator of the above character which will maintain its physical dimensions and characteristics after extensive use and over an extended period of time.

A further object of the invention is to provide an inkimpregnated applicator of the above character which is relatively inexpensive to manufacture.

Another object of the invention is to provide an ink applicator of the above character wherein the porous structure is made of a resin.

A further object of the invention is to provide an ink applicator of the above character in which the liquid vehicle of the ink with which the porous structure is impregnated is a plasticizer for the resin of the porous structure.

Another object of the invention is to provide an inkimpregnated applicator of the above character which is in the form of a roller.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the article possessing the features, properties, and the relation of elements, which are exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:

FIGURE 1 is a fragmentary side view of a printing I plate and an ink applicator such as are used in a postage metering machine.

FIGURE 2 is a flow diagram of the process of making an ink-impregnated applicator.

FIGURE 3 is a perspective view of an ink-impregnated porous roller made in accordance with the invention.

As shown in FIGURE 1, a typical printing plate 10 such as is used in a postage metering machine may be secured to a drum 24 and has a curved surface12 carrying the information to be printed. The surface 12 bears against a porous roller 14 which is rotatably supported at 16 for rotation against the printing plate surface 12 as the printing plate is rotated. It should be understood that although a porous roller is shown as the ink applicator, the invention is equally applicable to ink transfer structures having a fiat ink transfer surface.

As shown in the flow sheet of FIGURE 2, the ink roller is made by the following process. A powdered resin is mixed with a plasticizer (or combination of plasticizers) to form a plastisol of plasticizer and resin. Salt crystals are added to the plastisol in the proportion of two to twenty times as much salt, by weight, as plastisol. As will be described more fully hereinafter, the salt crystals form the pores of the porous structure and accordingly, the size of the salt crystals will determine the average size of the pores.

The plastisol and salt mixture is then molded in the desired shape under heat for a period of time. For an ink applicator the mold may be in the shape of a roller to form a salt-filled roller. The salt is then leached from the molded roller by hot water, leaving a porous resin roller. The porous roller is then impregnated with ink by a vacuum process wherein air is evacuated from and around the roller while the latter is immersed in ink and then the immersed roller is exposed to the atmosphere whereby the pores fill with ink. The inked roller thus produced is then ready for use as an ink transfer mechanism in a printing machine such as a postage metering machine.

As shown in FIGURE 3, the roller body 14 is provided with a shaft 16 which is journalled in support 18 (FIG- URE 1) to permit rotation of the roller when a printing plate or die rotatably contacts the roller surface. The ink-impregnated roller such as shown in FIGURE 3 should maintain its physical characteristics in dimension after thousands of ink transfer operations.

As an ink transfer structure, the roller should not vary appreciably in diameter nor should the resilience or texture of its surface vary over an extended period of time or use. It has been found that the principal cause of change in the physical characteristics or dimensions of such rollers is due to the ink vehicle in the porous body. As is well known, ink generally comprises a pigment or dye or combination thereof which is carried by a vehicle, the liquid medium with which the colorant is applied.

In the making of disposable ink-impregnated rollers, it has been found that polyvinyl chloride or copolymers thereof are preferred resins from which to make the roller body. As pointed out above, one of the initial steps in making the roller is to plasticize the resin. It has been discovered that by employing an ink vehicle of approximately the same chemical composition as that of the plasticizer or plasticizers used in making the-roller, the inkimpregnated roller will maintain its physical characteristics for very long periods of time and for extended use. Thus, the use of the resin plasticizer as an ink vehicle maintains the roller diameter within acceptable limits and also maintains roller resiliency .and the proper surface texture of the roller when used in printing ap paratus such as a postage metering machine.

The invention will now be described more specifically. In the process of making an ink-impregnated roller according to the invention, polyvinyl chloride and plasticizer are mixed in equal parts to form the plastisol. Granulated sodium chloride, preferably in cubicle form and of from 100-140 mesh in size, is then added to the plastisol in the proportion of two to twenty parts NaCl to 1 part plastisol, and preferably five to six parts NaCl to 1 part plastisol, by weight.

The plastisol-salt mixture is then molded into the shape of a cylindrical roller at from 300 to 450 F. for a period of from twenty minutes to one hour. The molded salt filled roller is then removed from the mold and is soaked in hot water. The hot water leaches the salt from the salt filled roller leaving a porous roller remaining. The roller may be further rinsed and dried and is then put under a vacuum. While under a vacuum the roller is immersed in ink and is then exposed to atmospheric pressure which fills the roller body with ink.

The ink vehicle is very important in maintaining the roller body in good condition to function as an ink applicator. Some ink vehicles, for example, tend to cause plasticizer migration, or to extract plasticizer or other constituents from the roller body. Further, the use of improper ink vehicles may cause excessive swelling of the roller which accordingly affects contact of the ink roller and printing plate. Still other ink vehicles tend to set on the roller surface or to cause brittleness in the roller body itself at the roller surface. Such ink vehicles are unacceptable for use in many business machines since the inking roller must remain in good condition for a substantial period of time.

In one particular case (see FIGURE 1), the interference between the printing plate surface 12 and roller surface 20 at point 22 should be from .020 to .070 inch for uniform inking of the printing plate. In other words, the plate surface 12 deforms the roller surface 20 slightly at point 22 to insure good contact over the plate surface and to gently squeeze ink from the roller pores.

If the roller swells excessively, the roller will interfere too much with the printing plate, resulting in excessive inking and accelerated deterioration of the inking roller. If the roller shrinks, the printing plate .will be unevenly inked, if at all. Hardening or setting of the roller surface 20 also results in closure of the roller pores and poor ink transfer because the pore squeezing action is adversely affected.

I have discovered that an ideal ink vehicle should approximate the composition of the roller body plasticizer or plasticizers. In those cases where a combination of plasticizers are used, a substantial amount of at least one of the plasticizers should be present as the ink vehicle. When ink vehicles which are the same as the plasticizer for the roller body are used, I have found that the surface texture and resiliency of the rollers, as well as the physical characteristics and dimensions, are unchanged after thousands of ink transfer operations and after many months of use.

The following specific examples are illustrative of the invention.

Example 1 One hundred parts of polyvinyl chloride resin were mixed with one hundred parts by weight of a plasticizer composed of dioctyl phthalate and 25% Conoco H-35. Conoco H-35 is a synthesized alkyl aryl hydrocarbon having a molecular weight of 280. After thorough mixing of the polyvinyl chloride resin and plasticizer combination, 5 parts of tribasic lead sulfate (hydrous) was added thereto as a stabilizer. The plastisol thus formed was then combined with cubicle sodium chloride crystals of from 140 mesh in size (-150 microns) in the proportions 85% NaCl to 15% plastisol by weight. The plastisol-NaCl mixture was then molded in the form of a roller at 350 F. for forty-five minutes. The salt-filled roller was removed from the mold and leached with hot water to remove the salt and provide a porous roller body. The porous roller body was then filled with ink by vacuum. The ink vehicle was made up to 75% dioctyl phthalate and 25% Conoco H-35, the same constituents and proportions as used for the resin plasticizer.

Example 2 The same procedure as in Example 1 was followed except that the plasticizer and ink vehicle were both composed of 80% dioctyl phthalate and 20% Mobilsol L, a petroleum fraction with an approximate molecular weight of 267, boiling range 520 F. to 769 F. and a carbon atom analysis weight percent of approximately C (aromatic) 12, C (naphthenic) 47 and C (parafiinie) 41.

Example 3 The same procedure was followed as in Example 1 except that the plasticizer and ink vehicle were both composed of a combination of 75% dioctyl phthalate and 25% naphthenic mineral oil.

Example 4 The same procedure was followed as in Example 1 above except that the plasticizer and ink vehicle were both composed of tricresyl phosphate.

The inks for all the above examples were of the following composition by weight:

Ink vehicle 89%; red pigment (barium lithol) 10%; wetting agent (lecithin) 1%.

Inked rollers made in accordance with the above examples were then inserted into postage metering machines for testing. Each roller made in accordance with the examples above was tested for at least four thousand printing impressions and showed excellent ink transfer characteristics after four thousand impressions. In all of the above examples the tested rollers showed only a slight degree of swelling but were Well within tolerable limits for such a use. Further, the texture and resiliency of the roller surfaces of all four examples above remained substantially uniform over a period of several months with no setting or caking of the roller surface, and with no plasticizer migration or extraction evident in the roller body itself.

Thus, an ink-impregnated roller made in accordance with the invention is particularly suitable for use in business machines. Further, as a matter of economics, such a roller may be disposable since thousands of printing impression can be made from a single roller.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efiiciently attained and, since certain changes may be made in the above article without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention which, as a matter of language, might be said to fall therebetween.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. An ink applicator comprising, in combination,

A. an ink containing porous body,

' (1) said body being made principally of po1yvinylchloride resin, and (2) a liquid plasticizer for said resin, B. an ink contained in the pores of said body,

(1) said ink having a colorant in a liquid vehicle, (a) said ink vehicle being of essentially the same composition as said plasticizer, whereby the physical dimensions and characteristics of said ink applicator are maintained within predetermined limits over a substantial period of use and time.

2. An ink applicator comprising, in combination, A. an ink containing porous body,

(1) said body being made principally of polyvinylchloride resin, and (2) a liquid plasticizer system for said resin com- (a) a liquid plasticizer for said resin in combination with (b) a liquid hydrocarbon diluent, B. an ink contained in the pores of said body,

(1) said ink having a colorant in a liquid vehicle, (a) said ink vehicle being of essentially the same composition as said plasticizer system, whereby the physical dimensions and characteristics of said ink applicator are maintained within predetermined limits over a substantial period of use and time.

3. An ink applicator comprising, in combination, A. an ink containing porous body,

(1) said porous body being made of a resin,

(a) the major portion of said resin being polyvinylchloride,

(2) a liquid plasticizer for said resin containing a major portion taken from the group consisting of (a) dioctylphthalate and (b) tricresylphosphate B. an ink contained in the pores of said roller,

(1) said ink comprising,

(a) a colorant and (b) a liquid vehicle of essentially the same composition as said plasticizer, whereby the physical dimensions and characteristics of said ink applicator are maintained within predetermined limits over a substantial period of use and time.

4. An ink applicator as defined in claim 3 wherein said plasticizer includes a minor portion of a liquid hydrocarbon diluent in combination with said major portion of said plasticizer.

5. An ink applicator as defined in claim 4 wherein said liquid hydrocarbon diluent is an alkyl aryl hydrocarbon having a molecular weight of approximately 280.

6. An ink applicator as defined in claim 4 wherein said liquid hydrocarbon diluent is a petroleum fraction having an approximate molecular weight of 267 and a boiling range of approximately 520 to 769 F.

7. An ink applicator as dfined in claim 4 wherein said liquid hydrocarbon diluent is a mineral oil.

8. The method of making an ink applicator, comprising the steps of,

A. combining a polyvinylchloride resin and a liquid plasticizer for polyvinylchloride to form a plastisol,

B. intermixing with said plastisol a granular material therewith,

(1) said granular material being non-reactive with said plastisol, and (2) said granular material being soluble in a solvent substantially non-reactive with the plastisol constituents,

C. molding said plastisol and granular material in the shape of an ink applicator body,

D. dissolving said granular material from the molded body with a solvent to form a porous body,

(1) said solvent being substantially non-reactive with the porous body,

E. subjecting the porous body to a partial vacuum,

F. immersing the porous body in an ink,

(1) said ink comprising a vehicle and a colorant in the vehicle,

(a) the ink vehicle being of essentially the same composition as said plasticizer, G. and then subjecting the submerged porous body to atmospheric pressure to fill the pores of the body with said ink.

References Cited by the Examiner UNITED STATES PATENTS 2,371,868 3/1945 Berg etal.

2,392,521 1/1946 Chollar 101-327 2,620,730 12/1952 Gilbert 101-367 2,631,358 3/1953 Hill.

ROBERT E. PULFREY, Primary Examiner.

DAVID KLEIN, Examiner.

JANYCE A. BELL, Assistant Examiner. 

2. AN INK APPLICATOR COMPRISING, IN COMBINATION, A. AN INK CONTAINING POROUS BODY, (1) SAID BODY BEING MADE PRINCIPALLY OF POLYVINYLCHLORIDE RESIN, AND (2) A LIQUID PLASTICIZER SYSTEM FOR SAID RESIN COMPRISING, (A) A LIQUID PLASTICIZER FOR SAID RESIN IN COMBINATION WITH (B) A LIQUID HYDROCARBON DILUENT, B. AN INK CONTAINED IN THE PORES OF SAID BODY, (1) SAID INK HAVING A COLORANT IN A LIQUID VEHICLE, (A) SAID INK VEHICLE BEING OF ESSENTIALLY THE SAME COMPOSITION AS SAID PLASTICIZER SYSTEM, WHEREBY THE PHSICAL DIMENSIONS AND CHARACTERISTICS OF SAID INK APPLICATOR ARE MAINTAINED WITHIN PREDETERMINED LIMITS OVER A SUBSTANTIAL PERIOD OF USE AND TIME. 